Although their noun/verb differences have been covered in other posts, is there any specific difference between using them as nouns only?
For example, is there any difference between:
城市已经发生了很大的变化。
城市已经发生了很大的改变。
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Sign up to join this communitya. 城市已经发生了很大的变化。
b. 城市已经发生了很大的改变。
Comparing 变化 with 改变 in this context, 改变 connotes 城市 is being changed (say by people) from the past. Well, 变化 connotes that we see or identify some difference from what the city used to be. 改变 describes the action, change.
变化 is a noun only, 改变 is a verb commonly, but also a noun. They are interchangeable as a noun in most cases, 改变 usually carries the meaning of positive changes.
改变 always means a better change than before. 变化 just means something changed, it could be better or worse than before.
The meaning are the same. No matter which word you choose, no native Chinese speaker will give it a second glance.
That being said, I believe typical Chinese will automatically choose 变化 for appearance changes, and 改变 for behavior or character changes. Particularly, we say "孙悟空有七十二般变化。" We never say "孙悟空有七十二般改变。"
变化 is usually only used on inanimate objects. 改变 can be used on people. Like usual, the difference is not set in stone.
昨天和不見數年的老朋友吃飯,他改變了很多
改变 means to change something or someone by others. For example, 艰苦的生活改变了他的性格. 今年公司改变了一些规章制度.
变化 means transformation. It is a process of the change of something. It implys the difference between now and then. For example, 这座城市发生了很大的变化.
Those two words can be used exchangably. For example, 生活有了很大的变化. 生活有了很大的改变. 生活有了很大的改进. All means the same.
变化 happens objectively , 改变 happens subjectively (even in your example the object is omitted).